1. Field of the Invention
This invention relates to an apparatus for transistor mounting in a high power microstrip circuit to improve heat spreading and reduce parasitic effects.
2. Description of the Prior Art
Transistors used in high power microstrip applications generally rely on torqued screws to achieve low thermal contact resistances in transferring dissipated power into a circuit carrier block or into a slot formed in the carrier block for mounting the transistors. Circuit performance is dependent not only upon the intimate contact between the carrier block and the mounting surface of the transistor, but also on the intimate contact between the ground plane of the substrate and the block. Voids between these surfaces introduce undesirable parasitics and vary the impedance match into the transistor to thereby detune the circuit.
Prior art arrangements are dependent upon a metallic contact between the substrate ground plane and the carrier block, solder being used for this purpose. Because of the impurities of the solder and the entrapment of gases upon melting of solder, voids and air gaps commonly occur. The voids and air gaps detrimentally affect the circuit impedance resulting in a degradation of circuit performance and reduction of reproducibility.